In U.S. Pat. Nos. 4,154,448 and 4,208,056, there is set forth a rotating blowout preventor, hereinafter called a RBOP, having a washpipe rigidly affixed to a main body, with there being a bearing housing located externally of the washpipe for rotatably supporting a rotating head assembly. The rotating head assembly includes a removable stripper rubber assembly which is received within the washpipe and is clamped at the upper end of the rotating head assembly. The stripper rubber assembly accordingly is easily removed from the remainder of the RBOP by merely unclamping the clamp means and lifting the unitary stripper rubber assembly from the interior of the washpipe.
The above construction isolates the bearing housing from the returned drilling fluid. However, debris flowing uphole impact against the annulus formed between the stripper rubber exterior and the washpipe interior. The debris continually and progressively accumulates and eventually the interior of the washpipe becomes unduly erroded. As this undesirable condition progresses, the debris eventually attack the rotating seal, accelerating the wear on the seal, until eventually the RBOP must be repaired. This condition is especially pronounced when drilling with compressible fluid such as air or gas because the debris can rebound several times as the drilling fluid changes direction to flow through the lateral outlet passageway.
Accordingly, it would be desirable to provide a RBOP with means by which the debris are deflected from an uphole axial direction into a lateral direction so that impact against the intervening area between the stripper rubber and the interior surface of the washpipe is procluded, thereby greatly reducing wear on the RBOP. Such an improvement is the subject of the present invention.